Yaskawa MP940-MW+ - Manual (Page 15)

TECHNICAL NOTE
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The timer block, while it has two out ports, the false port should always be looped back to the in
port of the block. Time only accumulates while the block is being executed, thus the need for the
loop back. If items are connected between the false port and the in port, it can cause the timer to
take additional time to complete. For example, if a block is inserted between the false port and
the return to the true port, and it takes one scan to execute that block, the amount of time will be
doubled. One last thing to remember about the Timer block is that the time value in it is retentive.
In other words, if the timer starts timing and for some reason gets interrupted, (program is halted,
etc) upon re-entering said timer block it will finish timing.
There is an alternative way to construct a timer. A system variable exists, mTime, this
variable increments every high scan. A user can capture the value of mTime in a set variable
block. In the next block, an If Event block, compare if mTime > CaptureTime + DesiredTime.
While that condition is false the program can monitor other events and return to the in port of the
If Event block. Be careful with this method, as the timed value can vary if there is a lot of logic
between the false port and the return to the in port.
06 Gear
The Gear subroutine is fairly straightforward, for discussion purposes it is broken down
into two sections. The two sections include: Engaging/Disengaging, and Running.
Engaging/Disengaging
Blocks 3 –
4 & 7 – 9 comprise
engaging and
disengaging of
gearing. Blocks 3
and 9 take care of
activating /
deactivating
Output 6 while entering / leaving gearing subroutine. The key element to remember is after the
disengage block include a stop block. If the stop block is not included and the slave is
disengaged while the master is motion, the slave will continue to gear to the last known
calculated speed of the master axis. Additionally, the stop block will switch the axis to position
mode, allowing a controlled deceleration to zero speed and will maintain position once stopped.